Method of making a uranium-antimony oxide catalyst

ABSTRACT

AN IMPROVED OXIDATION AND/OR AMMOXIDATION CATALYST BASED ON ANTIMONY, URANIUM AND OXYGEN IS PREPARED BY FORMING A SOLUTION OF SOLUBILIZED ANTIMONY OXIDES AND URANIUM SALTS OR OXIDES, EVAPORATING THE SOLUTION TO DRYNESS TO FORM A SOLID RESIDUE, DRYING THE SOLID RESIDUE AND HEATING THE DRIED SOLID RESIDUE AT A TEMPERATURE OF FROM 750* C. TO 1000* C. A PREFERRED EMBODIMENT REPRESENTED CATALYST CONSISTING ESSENTIALLY OF A COMPOUND REPRESENTED BY THE FORMULA USB3O10. THE CATALYST IS USEFUL IN OXIDIZING AND AMMONOXIDIZING OLEFINS.

United States Patent 3,816,596 METHOD OF MAKING A l UM-AONY OXIDE CATALYST Kenneth V. Wise, Ballwin, Mm, assignor to Monsanto Company, St. Louis, M0. N0 Drawing. Filed Oct. 4, 1971, Ser. No. 186,535 Int. Cl. 001g 43/00 US. Cl. 423-253 3 Claims ABSTRACT OF THE DESCLOSURE BACKGROUND OF THE INVENTION This invention relates to an improved oxidation and/ or ammoxidation catalyst system containing the elements antimony and uranium and to an improved method for preparing such catalyst system.

It is well known that olefins can be oxidized to oxygenated hydrocarbons such as unsaturated aldehydes and acids, for example, acrolein and methacrolein, acrylic and methacrylic acid. It is also well known that olefins can be ammoxidized to unsaturated nitriles such as acrylonitrile and methacrylonitrile. The value of such oxygenated hydrocarbons and unsaturated nitriles is generally well recognized with acrylonitrile being among the most valuable monomers available to the polymer industry for producing useful polymeric products.

Various catalytic processes are known for the oxidation and/ or ammoxidation of olefins. Such processes commonly react and olefin or an olefin-ammonia mixture with oxygen in the vapor phase in the presence of a catalyst. For the production of acrolein and acrylonitrile, propylene is the generally used olefin reactant and for the production of methacrolein and methacrylonitrile, isobutylene is the generally used olefin reactant.

A catalyst system composed of the oxides of antimony and uranium and the oxidation and ammoxidation of olefins using such catalyst has been described in United States Letters Patent Nos. 3,198,750 and 3,308,151. These patents describe preparation of the catalyst by precipitation wherein the oxides of the elements are contained in a slurry which is filtered to remove soluble salts and recover the catalytic components as the filter cake.

In the catalytic oxidation and/ or ammoxidation of olefins, the commercial utility of a catalyst system is highly dependent upon the cost of the system, the conversion of the olefin and the yield of the desired product. In many cases a reduction in the cost of a catalyst system in the order of a few pennies per pound or a 1% increase in the yield of a desired product represents a tremendous commercial economical savings. Accordingly, research eiforts are continuously being made to define new or improved methods of making such catalyst systems to reduce the cost and/or to upgrade the activity and selectivity of such catalyst systems in particular processes.

SUMMARY This invention is directed to improving the activity and selectivity of a catalyst system containing the elements antimony and uranium for the catalytic oxidation and/or Patented June 11, 1974 ammoxidation of olefins and is particularly directed to an improved method of making such catalyst system.

Accordingly, typical objects of this invention are to provide: 1) an improved oxidation and/or ammoxidation catalyst system containing oxygen, antimony and uranium, (2) an improved process for the preparation of a catalyst system containing oxygen, antimony and uranium, (3) an improved oxidation and/or ammoxidation catalyst system containing a substantially intermolecuar compound of oxygen, antimony and uranium, and (4) an improved olefin conversion process.

Other objects, aspects and advantages of this invention will become apparent to those skilled in the art upon further study of this disclosure and the appended claims.

In accordance with this invention, the catalytic activity and selectivity of a catalyst system containing oxygen, antimony and uranium are greatly enhanced by preparing a solution having antimony oxides and uranium salts or oxides dissolved therein, evaporating the solu tion to form a solid residue, drying the solid residue and heating the dried solid residue at selected elevated temperatures to form the active catalytic components.

The catalyst of this invention is based primarily on the elements antimony and uranium in combination with oxygen, however, it may include other additional elements, such as phosphorous, as well as oxides or antimonates of other materials, such as nickel, vanadium, barium, silicon and the like.

The antimony:uranium atomic ratio of the catalyst effective in the conversion of unsaturated hydrocarbons in accordance with this invention can. range from about 1:1 to about 99:1, preferably from about 1:1 to about 20:1 and more preferably at a ratio of about 3:1.

Antimony metal may be used as a starting material which is converted to the oxide by hot nitric acid. The antimony oxide is then solubilized by adding hydrochloric acid to the mixture. If antimony oxide is used as the starting material it may be dissolved in a mixture of nitric and hydrochloric acids. Uranium oxides or salts of uranium may be used as starting material.

After the antimony oxide and uranium oxide or salt are thoroughly dissolved to form a true solution, the solution is evaporated to dryness to form a solid residue of the catalytic components. The heating of the solution to cause evaporation can be conducted at a temperature of from about 30 C. to about C. A temperature of about 110 F. has been found to be satisfactory. The solid residue may be obtained by adding ammonium hydroxide to the solution instead of heating the solution.

After forming the solid residue from the solution of antimony oxide and uranium oxide or salt, the solid residue is dried. Drying of the solid residue can be obtained at a temperature of from about 100 C. to about 180 C. A suitable drying temperature is about C. However, the drying can be obtained at higher temperatures such as up to about 650 C. The time required for drying the solid residue can range from an hour up to about 64 hours. Obviously, the drying temperature selected will dicate the required drying time with the lower temperatures requiring the longer time. Also, the solid residue may be dried at different temperatures, for example at 110 C. for from 2 to 64 hours and then at a temperature of from about 250 C. to about 650 C. for from 2 to 24 hours.

After the solid residue is dried, it is further heated at an elevated temperature to otbain the active catalytic form of the elements. This calcination of the catalyst is conducted at a temperature in the range of from about 550 C. to about 1150 C. The time for calcination can vary and depends upon the temperatures employed. Generally, a time period of 2 to 24 hours at the designated temperatures is sufficient. The calcination may be conducted in the presence of oxygen (air); however, the catalyst may also be made active by calcining it in the absence of oxygen, such as in a nitrogen atmosphere.

It has recently been determined that the most active combination of antimony, uranium and oxygen for convetting an olefin and ammonia to nitrile is a compound having a nominal formula of USb O Generally speaking and heretofore, commercially available antimony and uranium oxide ammoxidation catalysts are composed of several detectable compounds, represented by the nominal formulas Sb O Sb O4, U303, USb3O1 and U Sb3O15, with the most active compound, USb 0 comprising only about 50 weight percent of the total catalyst.

A highly preferred embodiment of this invention is the preparation of a catalyst which consists essentially of an intermolecular compound or a single component having a nominal formula of USb O' Accordingly, an atomic ratio of 3:1 antimonyzuranium is preferred at this time.

When calcining a dried solid residue formed from a 3:1 ratio of anitmonyzuranium, it has been determined that the USb O combination is formed over a rather narrow temperature range. Below a temperature of about 750 C. such compound is not detected and above about 1000 C. such compound is transformed into less active compounds. However, within this temperature range the catalyst contains 98 to 100 weight percent of USb O The improved catalyst of this invention exhibits exceptional utility in the conversion of olefins with or without the presence of ammonia. The olefins employed as reactants for conversion by the catalyst of this invention may be open-chain as well as cyclic and include, for example, propylene, butene-l, butene-2, isobutene, pentene- 1, pentene-Z, 3-methyl butene-l, Z-methyl butene-2, hexene-l, hexene-2, 4-methyl pentene-l, 3,3 dimethyl butene- 1, 4-methyl pentene-Z, octene-l, cyclopentene, cyclohexone, and the like. Particularly, when the catalyst of this invention is used as merely an oxidation catalyst, it is particularly adapted to the conversion of propylene to acrolein and isobutylene to methacrolein. Of course, mixtures of olefins may be employed and mixtures of olefins with other hydrocarbons are applicable to the process of this invention. When the catalyst of this invention is to be used as an ammoxidation catalyst, the olefins as aforestated are applicable. However, the catalyst of this invention is particularly adapted to the conversion of propylene with ammonia and oxygen to acrylonitrile at 250 C. to 650 C.

The molar ratio of oxygen to the olefin in the feed will generally be in the range of 0.5 :1 to 4:1 with a preferred ratio being 1:1 to 3:1. The molar ratio of ammonia to olefin in the feed will generally be in the range of 0.5:1 to 5:1 and preferably slightly over the stoichiometric ratio of 1:1 ammonia:olefin will be employed.

While ammonia is most generally employed as the nitrogen providing compound, other nitrogen containing materials may be employed which decompose to produce reactive nitrogen under the reaction conditions. Any source of oxygen, pure or in admixture with inerts, may be employed in the process of this invention. Air is a satisfactory source of oxygen for use in this invention.

. The improved catalyst system of this invention can be further improved by washing the dried solid residue with water, filtering the solid residue from the wash, redrying the recovered solid residue and then heating the dried solid residue at elevated temperatures to form the active components.

The catalyst system of this invention can be advantageously employed for synthesizing styrene from ethylbenzene and oxygen, butadiene from butenes and oxygen, acrolein or methacrolein from propylene or isobutylene and oxygen, acrylonitrile or methacrylonitrile from propylene or isobutylene, ammonia and oxygen, isoprene 4 from 2-methyl butene-2 and oxygen, and 2-cyano-1,3- butadiene from 2-methyl butene-Z or isoprene, ammonia and oxygen.

Suitable salts of uranium useful as the starting material in this invention are, for example, uranium tetra- .chloride, tetrabromide or tetraiodide, uranium pentachloride, uranium hexafluoride, uranyl nitrate, uranyl acetate, uranyl sulfate, uranyl chloride and uranyl bromide. Oxides of uranium may be used as the starting material.

DESCRIPTION OF PREFERRED EMBODIMENTS The following Examples are presented as illustrative of the invention and, as such, are not intended to be restrictive upon the specific materials, quantities and operating variables specifically set forth therein.

EXAMPLE I A catalyst system composed of antimony and uranium having an Sb:U atomic ratio of 3:1 is prepared as follows: 160 grams of Sb metal is added to 600 ml. of hot 70% nitric acid. After evolution of nitrogen oxides cease, 600 ml. of 37% hydrochloric acid is added and the slurry is heated and stirred until the Sb O is in solution. A second solution is prepared by dissolving 121.5 grams of U 0 in 250 ml. of hot 70 HNO The two solutions are mixed. The resulting solution is heated until a suspension is formed and the heating is continued until the suspension is concentrated and thickens. The concentrated suspension is dried at 110 C. for 16 hours and then calcined in air at 875 C. for 16 hours.

EXAMPLE II Example I is repeated except that after the suspension is dried at 110 C. for 16 hours it is washed repeatedly with water until the washings read neutral to litmus paper. Each Washing comprised pouring water onto the catalyst (250 ml. of water per 60 grams of catalyst), stirring the mixture, letting the mixture set for a minimum of 5 minutes, and decanting the liquid. The catalyst is then calcined in air at 875 C. for 16 hours.

EXAMPLE III Example I is repeated except that after the suspension is dried at 110 C. for 16 hours, water is added to the catalyst ml. of Water per 60 grams of catalyst) and the mixture is stirred. Then 28% NH OH is added to the mixture (30 m1. of 28% NH OH per 60 grams of catalyst) and the mixture is stirred. The pH of the mixture is 4. After decanting a yellow colored liquid, the catalyst is calcined in air at 875 C. for 16 hours.

EXAMPLE IV A catalyst system composed of antimony and uranium having an Sb:U atomic ratio of 3:1 is prepared as follows: 30 grams of Sb metal is added to 115 ml. of hot 70% nitric acid. After evolution of nitrogen oxides cease, 115 ml. of 37% hydrochloric acid is added and the slurry is heated and stirred until the Sb O is in solution. A second solution is prepared by dissolving 40.8 grams of UO (NO .6H O in 45 ml. of 70% NHO The two solutions are mixed and then added to 450 ml. of 28% ammonia hydroxide. The pH of the mixture is 5. The resulting slurry is filtered and 250 m1. of water is added to the filter cake. After standing 10 minutes the slurry is filtered. The filter cake is dried at C. and then calcined in air at 875 C.

EXAMPLE V A catalyst system composed of antimony and uranium having an Sb :U atomic ratio of 3: l is prepared as follows: 30 grams of Sb metal is added to ml. of hot 70% nitric acid. After evolution of nitrogen oxides cease, 115 ml. of 37% hydrochloric acid is added and the slurry is heated and stirred until the Sb is in solution. A second solution is prepared by dissolving 40.8 grams of 70% HNO After evolution of nitrogen oxides the slurry is filtered and the filter cake antimony oxide is washed with water until the filtrate is neutral. The antimony oxide is then dissolved in 575 ml. of hot 37% HCl. A second solution is prepared by dissolving 204 grams of in 45 ml. of 70% NHOQ- The two solutions are mixed 5 and the pH is adjusted to 6 by adding 410 ml. of 28% U0 (NO 6H 0 ammonia hydr-oxlde' The rfa'sultmg- Slurry filtered in 50 ml. of hot 37% HCl. The two solutions are mixed the filter cake 1s washed 3 times w1th 120 ml. of portlons of water. The filter cake is dried at 110 C. and then and the PH adlustid to 7 y addmg 1680 of 20% calcined in air at C 10 l IH O I-I. The resulting slurry 1s filteredand the filter cake 1s broken up and stirred for 10 minutes in 2 llters of water. EXAMPLE VI The slurry is then filtered and the filter cake is dried at 110 C. A portion of the catalyst is calcined in air at 850 haeinig ii s b z l l ai t o fih i :f g i il geggi 2 for 16 hours. Another portion of the catalyst is calcined lows: 30 grams of Sb metal is added to 115 ml. of hot 15 mtrogenfit for 16 hours- 70% nitric acid. After evolution of nitrogen oxides cease, AS i 1n h examples the followmg terms have the 115 ml. of 37% hydrochloric acid is added and the slurry followmg defimtlons: is heated and stirred until the Sb O is in solution. A second solution is prepared by dissolving 40.8 grams of Percent propylene (C H converted UO (NO 6H O 20 mole C Ha in feed-mole 0 11 in effluent 100 in 45 ml. of 70% HNO The two solutions are mixed and mols m feed the P is adjfsted to 8 by 0f 28% Percent selectivity to acrylonitrile (AN) monia hydroxlde. The resulting slurry is filtered and the filter cake is dried at 110 C. and then at 180 C. for 24 25 mo1s AN m effluent X 100 hours. The catalyst is calcined in air at 430 C. for 64 mols feed-H1015 efiiuent hours and then at 875 C. for 16 hours. Percent propylene to acrylom-trfle EXAMPLE VII mols AN formed X100 A catalyst system composed of antimony and uranium mole C 11 in feed having an Sb:U atomic ratio of 3:1 is prepared as follows: 90 grams of Sb metal is added to 345 m1. of hot Percent selectlvlty acrolem (ACR) 70% nitric acid. After evolution of nitrogen oxides cease, mols ACR in efiluent X 100 345 ml. of 37% hydrochloric acid is added and the slurry 1 0 in f d- 1 (3 11 in emuent is heated and stirred until the Sb O is in solution. A second solution is prepared by dissolving 122.4 grams of The apparatus employed in carrying out the runs in this UO (NO ,6H O in 135 m1, of 70% HNO The t o example is a fluidized bed type reactor. The reactor consolutions are mixed and the pH is adjusted to 8 by adding sists of a 14 mm. inside diameter 96% quartz glass tube 1340 ml. of 28% ammonia hydroxide. The resulting fitt at t bottom With a fritted disc Supporting a slurry is filtered and the filter cake is washed 3 times with catalyst bed of up to 30 ml. in volume and fitted at the 500 ml. portions of Water. The filter cake is dried at 110 top With another fritted disc to remove entrained catalyst C, d then l i ed i i at 875 C. from the reactor efliuent. A thermowell of 4 mm. outside diameter 96% quartz glass extends through the center of EXAMPLE VIII the catalyst bed to the fritted disc. The reactor tube is A catalyst system composed of antimony and uranium jacketed with a larger tube in which sand is fluidized for having an Sb:U atomic ratio of 3:1 is prepared as folproviding even heat distribution. The entire reactor aslows: 90 grams of Sb metal is added to 345 ml. of hot sembly is placed in a controlled, hinged tube furnace. The 70% nitric acid. After evolution of nitrogen oxides cease, reactant gases are premixed and heated to about 475 C. 345 ml. of 37% hydrochloric acid is added and the slurry before entering the bottom of the reactor through a single is heated and stirred until the Sb O is in solution. A secinlet tube. The efiiuent gases from the reactor are heated ond solution is prepared by dissolving 122.4 grams of to prevent condensation prior to chromatographic anal- UO (NO .6H O in 135 ml. of 70% HNO The two ysis. solutions are mixed and the pH is adjusted to 8 by adding EXAMPLE X 1280 ml. of 28% NH OH. The resulting slurry is filtered and the filter cake is washed 3 times with 500 ml. portions The unsupported antlmonynuramum catillysts of EX- of water The filter cake is dried at 110 C A ortion of amp 16S I through-IX are used I]? cmiverslon of Propylthe catal st is calcined in air at 875 C for 16 hours em amnion-1a to acrylommle usmg the apparatus Another yortion of the catal St is calcified in mm) prev1ously described. The particle size of the catalyst at 8750 y g ranges from 74 to 250 microns in diameter. The weight EXAMPLE IX of the catalyst used in each run is 30 grams. The feed materials are carried in helium. The reaction temperatures A catalyst system composed of antimony and uranium are 470 to 480 C. and the pressure employed is atmoshaving an Sb:U atomic ratio of 3:1 is prepared as folpheric. Other process data and the results are given in lows: 150 grams of Sb metal is added to 575 ml. of hot Table I.

TABLE I Catalyst Example I Example II Example III Feed composition (volume percent) Oxyge 15.0 15.0 15.0 15.0 15. 03 15. 03 15. 03 15.2 16.2 15.2 Ammonias. 5 s. 5 s. 5 8. 5 10. 0s 10. 0s 10. 0s 9. s7 9. s7 9. s7 Propylene. 7. 4 7. 4 7. 4 7. 4 8. 92 s. 92 8. 92 s. 67 s. 57 a. 57 Contact time (gm. sec/m1. at STP) 10.0 10.0 10.0 10.0 10.0 10.0 10.0 9. 9 9. 9 9. 9 Elapsed reaction time (minutes) 2 32 62 92 5 35 10 40 Percent propylene convertednn 95. 4 90. 0 88. 2 87.2 92. 0 90. 9 91. 7 94. 4 95. 0 94. 8 Percent selectivity to acrylouitri 57. 5 77. 4 so. 0 81.0 27. s 86. a 86.7 84. 2 83.9 83. 9 Percent propylene to acrylonitrile 54. 4 69.7 70.6 70. 5 so. 4 78.5 79.0 79. 4 79. 7 79.5 HCN produced (volume percent) 0. 35 0. 29 0.28 0. 27 0. 42 0. 53 0. 55 0. 46 0. 57 0. 57

See footnotes at end of table.

TABLE I-Continued Catalyst..- Example IV Example V Example VI Feed composition (volume percent) 16. 85 16. 85 16. 93 16. 93 16. 93 16. 93 17. 35 17. 35 17. 35 17. 35 10.02 10. 02 10. 06 10.06 10. 06 10. 06 10. 10 10. 10 10. 10 10. 10 8. 68 8. 68 8. 72 8. 72 8. 72 8. 72 8. 85 8. 85 8. 85 8. 85 9. 9 9. 9 15. 1 15. 1 15. 1 15. 1 15. 1 15. 1 15. 1 15. 1 35 65 35 95 125 Start 30 60 90 Percent propylene converted 96. 6 95. 7 96. 99. 7 99. 8 99.8 100. 99. 2 99. 3 98. 7 98. 8 Percent selectivity to acrylonitrile. 79. 7 80. 8.08 83. 2 82.8 83. 2 82. 9 82. 4 82.0 83. 2 88. 3 Percent propylene to acrylonitrile 76.8 77. 1 77. 6 82. 8 82. 7 82.9 82.9 81. 8 81. 4 82.2 82.2 HON produced (Volume percent) 0. 27 0. 48 0. 48 0. 27 0.32 0. 27 0. 27 0.37 0. 32 0. 26 0.23

Example VIII Example IX Catalyst Example VII Air calcined 1 N2 calcined 1 Air calcined 3 N2 calcined 4 Feed comppsition (volume percent)' Oxyge 16. 73 16. 73 16. 73 16. 95 16. 95 16. 95 16.95 16. 95 16.97 16. 97 16.97 17. 12 17. 12 17. 12 Ammonia 9. 87 9. 87 9. 87 9. 55 9. 55 9. 55 9.55 9. 55 9. 88 9. 88 9. 88 9. 88 9. 88 9.88 Propylene. 8. 66 8. 66 8. 66 8. 88 8. 88 8. 88 8. 88 8. 88 8. 84 8. 84 8. 84 8. 83 8. 83 8. 83 Contact time* (g 14. 7 14. 7 14. 7 15.1 15.1 15.1 15. 1 15.1 9. 9 9. 9 9. 9 9. 9 9. 9 9. 9 Elapsed reaction time (minutes) 70 130 10 40 70 5 25 5 35 95 5 35 65 Percent propylene converted.-. 95. 7 96. 5 96. 6 96.5 95. 5 95. 3 95. 5 94. 5 93. 8 93. 5 93. 3 96. 0 96. 0 95.8 Percent selectivity to acrylonitri 83. 5 83. 7 84. 0 79. 2 80. 8 80. 1 72. 9 73. 8 81. 7 82. 2 83. 0 82. 3 80. 1 79. 8 Percent propylene to acrylomtnla. 79. 9 80.8 81. 2 76. 5 76. 3 76. 2 69.6 69. 7 76.5 76.8 77. 4 79. 0 76.8 76 4 HCN produced (volume percent) 0.31 0. 31 0. 31 0.27 0.25 0.23 0 0 0.58 0.67 0. 64 0.21 0.24 0. 27

1 Surface area of 6.22 m. /gm., 98% USb O and 2% Sbz0 1 Surface area of 4.97 m. /gm., 95% USbaO and 5% 819205. l Surface area of 10 mfi/gm.

4 Surface area of 5.96 mfl/gm.

Contact time determined as:

Weight of catalyst (grams) Flow rate (ml/min.) at STP The above data clearly shows that the catalyst system prepared in accordance with this invention using air or nitrogen calcination exhibits activity, selectivity, and stability for converting propylene to acrylonitrile.

EXAMPLE XI A catalyst is made in accordance with the procedure used in Example VIII'and is calcined in air at various selected temperatures. XRD analysis of the resulting compositions are made. The criticality of the temperature used to calcine the catalyst to obtain predominantly a compound having the nominal formula of USb O is indicated by the following analysis:

TABLE II Calcination Catalyst temp., C. components 110 Sb O 550 Sb O 725 Sb O 98 wt. percent USb O 2 wt. percent Sb O 950 99 wt. percent USb O 1000 100 wt. percent USb O 1100 2 5 wt. percent USb O 75 wt. percent U Sb O 1200 100 Wt. percent U 0 The predominantly crystalline substantially intermolecular compound characteristic of the 3:1 antimony-uranium catalyst of this invention is indicated by X-ray diffraction patterns obtained using a copper K0: radiation source having a wave-length of 1.5418 A. and a Ni filter. Each sample analyzed having a size 44 microns is scanned from at 5 to 110 at a rate of change of 1/ minute. The major X-ray difiraction lines and relative intensities are indicated in Table III.

TABLE III Line din A. III;

EXAMPLE XII A catalyst is made in accordance with the procedure used in Example VIII and calcined in air at various selected temperatures. The paramagnetic susceptibilities of the resulting compositions are made by the Faraday method. Indicative results are given in the following table:

TABLE IV Bohr Surface magnearea, tons per Calcrnation temp., C. mF/gm. mole U Theoretically, 1 unpaired electron per atom is equivalent to 1.73 Bohr magnetons per mole. Thus, the uranium is about 95% pentavalent uranium. Accordingly, the antimony has a valence of 5 when in the most active catalytic state, i.e., USb O EXAMPLE XIII The unsupported antimony-uranium catalyst of Examples I, V, and VIII are used in the conversion of propylene to acrolein using the apparatus previously described. The particle size of the catalyst ranges from 74 to 250 microns in diameter. The weight of the catalyst used in each run is 3 grams. The feed materials are carried in helium. The reaction temperatures are about 500 C. and the pressure employed is atmospheric. Other process data and the results are given in Table V.

1 Surface area of 10 ml/gm.

1 Surface area of 5.96 mt/gm.

Contact time determined as:

Weight of catalyst (grams) Flow rate (m1./min.) at SIP It will be obvious to persons skilled in the art that various modifications may be made in the improved catalyst and process as described in this application. Accordingly, it is intended that all such modifications which reasonably fall within the scope of the appended claims are a part hereof.

What is claimed is:

1. The method of making a catalyst containing a catalytic active compound of antimony, uranium and oxygen which comprises forming an acidic solution of antimony oxides and uranium salts or oxides, the atomic ratio of antimony to uranium being Within the range of from about 1:1 to about 99:1, forming a solid residue from said acidic solution by heating the acidic solution to cause evaporation or by adding ammonium hydroxide to the acidic solution to cause precipitation, drying the resulting solid residue, and heating the solid residue at a temperature of from about 550 C. to about 1150" C. to form said active compound.

2. The method of making a catalyst consisting essentially of a compound represented by the formula USb O by forming an acidic solution of antimony oxides and uranium salts or oxides, the atomic ratio of antimony to uranium being about 3:1, forming a solid residue from said acidic solution by heating the acidic solution to cause evaporation or by adding ammonium hydroxide to the acidic solution to cause precipitation, drying the resulting solid residue, and heating the dried solid residue at a temperature of from about 750 C. to about 1000 C. to form said compound.

3. The method of claim 2 wherein said solution is formed by oxidizing antimony metal with nitric acid, adding hydrochloric acid to dissolve said antimony oxides, and adding to said solution uranium oxide or a uranium salt which converts to the oxide.

References Cited UNITED STATES PATENTS 3,198,750 8/1965 Callahan et al. 252--467 X 3,408,401 10/1968 Ball et a1. 252-467 X 3,157,461 11/1964 Gill et al 423253 CARL D. QUARFORTH, Primary Examiner R. L. TATE, Assistant Examiner US. Cl. X.R. 25230l.1 R, 467 

